Mesh not UV unwrapping well?
It looks like the normals are not consistent.

Those dark spots on the mesh are caused by flipped normals. By enabling face normals display in 3D view > Properties region > Mesh display > Normals, you will notice that they are pointing the wrong direction:



To fix this, select everything in edit mode (A) and press CtrlN.

Now all the normals should be facing outwards: